A wind turbine generator is an apparatus in which a rotor head including wind turbine blades receives wind power and rotates and, for example, a gear box increases speed of this rotation and drives a generator to thereby generate power. The rotor head including the wind turbine blades is coupled to the gear box and the generator in a nacelle set in an upper part of a tower (a column) via a main shaft. Therefore, to adjust the direction of the rotor head to a wind direction that always fluctuates (to set a rotor rotation surface to be right opposed to the wind direction), for example, in a wind generation apparatus of an up-wind type, it is necessary to yaw-rotate (rotate on a substantially horizontal plane) the nacelle on the tower to receive wind from the front of the rotor head.
In the above explanation, the rotor head and the nacelle, both of which are set in the upper part of the tower and coupled via the main shaft, are generally referred to as wind turbine unit.
In the conventional wind turbine generators, for example, a yaw driving apparatus is mounted on a large wind turbine having large blade length. This yaw driving apparatus is an apparatus that, for example, as shown in FIG. 10, yaw-rotates a large nacelle 3 with driving force of a yaw motor 50 and controls the yaw rotation such that a rotor rotation surface is set right opposed to a wind direction following the wind direction. Reference numeral 2 in the drawing denotes a tower, 3 denotes a nacelle, 3a denotes a nacelle base plate, 51 denotes a driving gear, 52 denotes a fixed gear, 53 denotes a roller bearing, and 54 denotes a yaw braking device. It would be also possible to employ a slide bearing instead of the roller bearing 53.
On the other hand, in the conventional wind turbine generators, as often seen in a small wind turbine having small blade length, there is also a wind turbine generator that does not have the yaw driving apparatus as a passive yaw.
In the yaw driving apparatus, according to an increase in size of the wind turbine generator, the yaw motor, the driving gear, and the like are also increased in size. Such an increase in size of the yaw driving apparatus causes hindrance of a reduction in size and weight of the nacelle because demands concerning complication of the nacelle base plate and a maintenance space increase.
Therefore, it is proposed that an angle command value obtained by adding a control command value around the yaw to a reference command value for offsetting load around a tower shaft that acts on wind turbine blades is calculated and pitch angle command values for the wind turbine blades are set on the basis of this angle command value. Specifically, since loads of the wind turbine blades are measured to control a pitch angle for each of the wind turbine blades and the wind turbine unit is rotated by using aerodynamic force acting on the wind turbine blades, it is possible to reduce the size of the yaw motor and reduce frequency of use. (See, for example, Patent Literature 1)